z02201 ZiLOG Semiconductor, z02201 Datasheet - Page 50

• Manufacturer Part Number: z02201
• Description: Z02201 V.22bis Data Pump With Integrated Afe
• Manufacturer: ZiLOG Semiconductor

Table 20. Modem Data Pump Word Definitions (Continued)
PS000904-0107
Register & Address
(hex)
Notch
01A2-1A6 below
Default
Value
Function and Explanation
Notch Filter Coefficients
These RAM locations contain the notch filter coefficients. The notch
filter is a biquad section (2nd-order IIR) used during simultaneous
transmission and detection of tones (Config register, bits 0–6
(MODE) is 4) to remove a single transmitted tone from the received
signal used by the tone detectors. See the section
Transmission and Detection of Tones
information.
The default values for these locations are 0, 0, 0, 0, and 0x4000
respectively. The default values cause the notch filter to not modify
the received signal used by the tone detectors. The data pump sets
these locations to their default values when the host sets Config
register, bits 0–6 (MODE) to 4 to begin simultaneous transmission
and detection of tones.
The host must not modify these locations unless Config register, bits
0–6 (MODE) is 4.
To calculate the coefficients to remove a frequency f from the
received signal, use these following formulae where,
r = pole radius (0
q
a
Location
Name
Formula
The cosine function is calculated in radians, not degrees.
Before writing the coefficients to data pump RAM, convert them to
the format used by the data pump by multiplying each coefficient by
16,383, and round to the nearest 16-bit signed integer. For example,
2.0 becomes 32,766 (0x7FFE), -1.0 becomes -16,383 (0xC001), -2.0
becomes -32,766 (0x8002).
These formulae determine the coefficients of a biquad section with
symmetric zeroes, a zero radius of 1.0, a pole radius of r, and pole
and zero frequencies of f Hz.
See Simultaneous Transmission and Detection of Tones on page -56
for more detail and notch filter coefficients for the default frequencies
detected by the discrete tone detectors.
= (1-2rcos(
= 2
p
f/9600, f is the frequency (Hz) to be removed, (0
q
-r
b2
0x1A2 0x1A3
)+r
2
2
£
)/(2-2cos(
r<1), 0.9 is recommended
b1
2rcos(
V.22BIS Data Pump with Integrated AFE
q
q)
)
)
a3
0x1A4
a
a2
on page 56 for more
-2
0x1A5
a
cos(
q
Simultaneous
)
a1
0x1A6
£
a
f<4800)
46